COMMIT makes permanent the changes resulting from all SQL statements in the transaction. The changes made by the SQL statements of a transaction become visible   to  other  user  sessions  transactions  that  start  only  after transaction is committed.

ddkdhar

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• Feb 18th, 2007

All dml operations done previsouly makes permanent in hte database

rampratap409

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• Dec 5th, 2006

Commit ends all previous transactions by making changes permanent in the datafile ( logicaly in tables)

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The  goal of the optimizer is to choose the most efficient way to execute a SQL statement.

sravan1

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• Dec 11th, 2006

The optimizer determines the most efficient way to use the tables and indexes to complete the request made by an SQL statement after considering many factors related to the objects referenced and the conditions specified in the query.

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The  combinations of the steps the optimizer chooses to execute a statement is called an execution plan.

sravan1

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• Dec 11th, 2006

The operations that the oracle server performs to execute a SQL statement.

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When it is committed or Rollbacked.

rampratap409

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• Dec 5th, 2006

Commit/rollback ends a transaction

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For  long  transactions  that  contain  many  SQL  statements, intermediate markers  or  savepoints  can  be  declared  which  can  be used to divide a transaction  into  smaller  parts.  This allows the option of later rolling back  all  work  performed  from  the current point in...

rampratap409

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• Dec 5th, 2006

SavePoint:  this is also a TCL command, which puts break points between DML statements so that you can rollback to any point and keeping some part of transaction in process.exampleupdate emp set ...

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ROLLBACK  retracts  any of the changes resulting from the SQL statements in the transaction.

rampratap409

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• Dec 5th, 2006

ROLLBACK:  This is just like UNDO in MSOFFICE but can not  REDO, means what ever changes You made after any commit/rollback or A DDL command they will not be saved into database . when rollb...

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A  Read-Only transaction ensures that the results of each query executed in the transaction are consistant with respect to the same point in time.

nanibabu

• May 23rd, 2006

it will reads the data firsrt and then executes the transaction

poornima

• Apr 11th, 2006

This is very nice job to clarify our doubts

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COST and RULE.

Chiranjeevi Manne

• Nov 9th, 2005

One can specify COST , RULE or CHOOSE for OPTIMIZER _MODE in init.ora file

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Rule-based and Cost-based.

The   OPTIMIZER_MODE   initialization  parameter  Statistics  in  the  Data Dictionary  the OPTIMIZER_GOAL parameter of the ALTER SESSION command hints in the statement.

CHOOSE,ALL_ROWS,FIRST_ROWS and RULE.

The  Optimizer  chooses  Cost_based approach and optimizes with the goal of best throughput if statistics for atleast one of the tables accessed by the SQL statement exist in the data dictionary. Otherwise the OPTIMIZER chooses RULE_based approach.

This  value  causes  the  optimizer to the cost-based approach for  all SQL statements  in  the session regardless of the presence of statistics and to optimize with a goal of best throughput.

Choosing an executing planbased on the access paths available and the ranks of these access paths.

Considering  available  access  paths  and  determining  the most efficient execution  plan  based  on statistics in the data dictionary for the tables accessed by the statement and their associated  clusters and indexes.